fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-MERGE-72553
- https://snyk.io/vuln/npm:atob:20180429
- https://snyk.io/vuln/npm:braces:20180219
- https://snyk.io/vuln/npm:cli:20160615
- https://snyk.io/vuln/npm:concat-with-sourcemaps:20180429
- https://snyk.io/vuln/npm:cryptiles:20180710
- https://snyk.io/vuln/npm:extend:20180424
- https://snyk.io/vuln/npm:hoek:20180212
- https://snyk.io/vuln/npm:lodash:20180130
- https://snyk.io/vuln/npm:minimatch:20160620
- https://snyk.io/vuln/npm:sshpk:20180409
- https://snyk.io/vuln/npm:stringstream:20180511
- https://snyk.io/vuln/npm:tunnel-agent:20170305

package.json

@@ -35,7 +35,7 @@
     "gulp-angular-templatecache": "^2.2.1",
     "gulp-clean-css": "^3.9.4",
     "gulp-concat": "^2.6.1",
-    "gulp-htmlhint": "^2.1.1",
+    "gulp-htmlhint": "^2.2.1",
     "gulp-istanbul": "^1.1.3",
     "gulp-jscs": "^4.1.0",
     "gulp-less": "^4.0.0",